In stormwater drainage systems, it is desirable to remove debris from the storm water before it is discharged into rivers, lakes, bays and the like. Floating debris can be a particular problem because it accumulates on the banks of rivers and shores of bays while heavier debris sinks to the bed smothering aquatic life and causing siltation.
Consequently these materials can badly degrade the environment. Unfortunately, due to sociological problems such debris now includes syringes which obviously represent a further public health risk problem. It is desirable therefore to try to remove debris from stormwater and this is usually accomplished by means of separator or pollutant traps that basically attempt to trap debris from stormwater by use of meshes, grates or the like. Unless these are specially configured they tend to clog up, thereby reducing their effectiveness. Another problem in removing debris from stormwater is that energy is lost from the flow and manifests itself as raised water levels upstream of the trap with possible local flooding. Present pollutant traps use walls and the like across the pipeline as a means of diverting the flow into the separator. As these obstruct the pipeline they can cause backing up during high flows raising upstream water levels and causing local flooding. If they are not regularly cleaned out, as is often the case, the accumulations of debris and litter can build up and block the pipeline with similar results.
An object of the invention is to provide a separator that largely overcomes the problems noted above. The separator of the invention may find application in other areas where it is necessary to separate debris from liquids such as in sewage systems, trade waste treatment or town water supplies.